1. Field of the Invention
This invention in general relates to photographic camera indicator apparatus and, more specifically, to a low scene light indicating arrangement which is particularly suitable for use with folding cameras having collapsible type viewing devices.
2. Description of the Prior Art
Photographic indicator apparatus for visually displaying various kinds of information in the field of view of a camera viewfinder to simplify camera operation and aid the photographer in obtaining sharp, properly exposed pictures are well-known in the photographic arts. Examples of the kind of information displayed include exposure values, exposure meter needles and corresponding scales, f-numbers and/or shutter speeds, matching needle exposure meters, signals indicating the existence of low available light conditions, and the like. With such information readily observable by the photographer prior to or while he is composing the content of the picture, the overall convenience of the picture taking process is markedly improved since the number of camera manipulations is generally reduced, and the reliability of obtaining quality photographs is also enhanced since the photographer can view essential camera and scene information superimposed more or less exactly on the scene of interest.
The structure and operation of apparatus by which visual information can be displayed in a camera viewfinder in general appears to depend on such factors as the nature of the camera exposure control system (automatic vs. manual); the type of viewfinder utilized (through-the-lens or independent); what information is considered essential for the operation of the particular camera; the form in which the information is available; and where the information is located in the camera in relation to where it can be seen.
For example U.S. Pat. No. 4,034,392, issued to Sunao Ishizaka et al. on July 5, 1977 and entitled "Exposure Indicator Device In A Single Lens Reflex Camera With A TTL Exposure Meter Contained Therein", discloses a single lens reflex camera having an optical arrangement which includes a pentaprism and a prismatic element associated therewith for providing an exposure indication visible within the field of view of the camera finder.
Other apparatus which are similar to Ishizaka et al. in that pentaprism type finders are utilized in combination with prismatic elements to display aperture or exposure values are described in U.S. Pat. No. 4,016,576 issued to Katsuhiko Nomura on Apr. 5, 1977; U.S. Pat. No. 4,021,830 issued to Kyusei Kanno on May 3, 1977; and U.S. Pat. No. 3,996,593 issued to Naoyuki Uno et al. on Dec. 7, 1976.
Another example of such apparatus is described in U.S. Pat. No. 3,583,300 issued to Bruce K. Johnson et al. on June 8, 1971 and entitled "Photographic Camera With Viewfinder". In Johnson et al. a camera is disclosed which has an independent, reversed Galilean type viewfinder and an associated periscope like arrangement whereby a distance focusing scale located on a manually rotatable lens bezel can be seen by a photographer as he views a scene.
However, none of the known viewfinder display arrangements of the prior art appear to solve the problem with which the present invention is concerned. In particular, the primary object of the present invention is to provide photographic apparatus that is particularly suitable for providing in a collapsible type viewing device of a folding reflex camera a visual indication that the available scene light is below a threshold value which normally requires the use of an artificial light source.
Other objects of the invention will in part be obvious and will in part appear hereinafter. The invention accordingly comprises the apparatus possessing the construction, combination of elements and arrangement of parts which are exemplified in the following detailed disclosure.